1. Field of the Invention
The present invention relates to an NOx reduction catalyst and an exhaust system using the same. More particularly, the present invention relates to an NOx reduction catalyst and an exhaust system using the same which improve purification efficiency of nitrogen oxide as a consequence of storing the nitrogen oxide contained in exhaust gas and releasing the stored nitrogen oxide when a reduction reaction of the nitrogen oxide is activated.
2. Description of Related Art
Generally, exhaust gas flowing out through an exhaust manifold from an engine is driven into a catalytic converter mounted at an exhaust pipe and is purified therein. After that, the noise of the exhaust gas is decreased while passing through a muffler and then the exhaust gas is emitted into the air through a tail pipe. The catalytic converter purifies pollutants contained in the exhaust gas. In addition, a particulate filter for trapping particulate material (PM) contained in the exhaust gas is mounted in the exhaust pipe.
A selective catalyst reduction (SCR) apparatus is one type of such a catalytic converter. In the selective catalyst reduction (SCR) apparatus, reducing agents such as urea, ammonia, carbon monoxide, and hydrocarbon (HC) react better with nitrogen oxide than oxygen.
According to an internal combustion engine at which such a selective catalyst reduction apparatus is mounted, additional injection of fuel is continuously performed according to an amount of the nitrogen oxide contained in the exhaust gas. Therefore, hydrocarbon slip may occur and fuel consumption may be increased.
In addition, in a case that a reducing agent is continuously supplied, an oxidation-reduction reaction also occurs continuously. Therefore, durability of the catalyst may be deteriorated by oxidation heat occurring in the oxidation-reduction reaction.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.